Implement the Cast operator for Gorgonia backend

[clarkmcc]

#206

[clarkmcc]

@owulveryck I'm getting an infinite loop error so I must be on the wrong track. If you have time to point me in the right direction, that would be awesome!

[iamazeem]

Hi, @clarkmcc,
Were you able to make it work?

[clarkmcc]

@iamazeem no sadly. I've started porting my models by hand to Rust, then compiling to WASM (like this). I did notice that https://burn.dev/ is supposed to be able export models as different formats but I haven't experimented with that yet.